Icosahedral capsids with a triangulation number T=7 are composed of 12 pentameric and 60 hexameric capsomeres for a total of 420 capsid proteins. Spherical viruses with T numbers greater than or equal to 7 are skewed. They are therefore described as either right- (dextro) or left- (laevo) handed.
Papillomaviruses and Polyomaviruses are composed of pentameric capsomeres for a total of 360 capsid proteins. Nevertheless their icosahedric structure is that of a T=7 capsid, with pentamers occupying hexameric places. These capsids are right handed (dextro) (Pubmed)
Icosahedric triangulation number is calculated following Caspar and Klug system (1962 PubMed)